1. Field of the Invention
This invention generally relates to power transmission devices. More specifically, the present invention relates to fishing reel power transmission devices in a fishing reel, in which power is transmitted from a first member that rotates to a second member.
2. Background Information
Fishing reels often employ a power transmission device including a dual-stepped gear in which a larger-diameter gear and a smaller-diameter gear are arranged coaxially.
For example, a level wind mechanism in a dual-bearing reel uses a power transmission device having: a drive gear mounted to a spool shaft; a dual-stepped gear mounted rotatably to a side face of a side plate of the reel unit and having a larger-diameter gear that meshes with the drive gear; and a driven gear that is attached to a worm gear of the level wind mechanism and meshes with the smaller-diameter gear of the dual-stepped gear. In the dual-stepped gear employed in the dual-bearing reel, both the larger-diameter gear and the smaller-diameter gear are straight-tooth gears; they have a construction that can be easily formed unitarily from a resin, and the manufacturing cost can be easily reduced.
The oscillating mechanism in a spinning reel employs, as disclosed in Japanese Unexamined Patent Publication No. 2001-321041, a power transmission device having a pinion gear, which serves as a drive gear for rotating the rotor, a dual-stepped gear the larger-diameter gear of which meshes with the pinion gear, and a driven gear that meshes with the smaller-diameter gear of the dual-stepped gear. Both the larger-diameter gear and the smaller-diameter gear of the dual-stepped gear employed in the spinning reel are helical-tooth gears (screw gears) and the helical teeth are oriented in different directions. Generally, the use of helical-tooth gears can suppress noise when rotating. In particular, when a gear meshes with a gear made of metal, such as a pinion gear, the use of a synthetic resin instead of metal can further suppress noise. However, if the orientations of helical teeth are different, it is difficult to form the dual-stepped gear integrally by molding. For this reason, the dual-stepped gear is usually manufactured by joining two gears that have been separately molded or gear-cut.
When the two gears are straight-tooth gears in the foregoing conventional configuration, it is difficult to suppress noise, although the manufacturing cost can be reduced since they can be formed unitarily. On the other hand, when the larger-diameter gear and the smaller-diameter gear have helical teeth and the orientations of the helical teeth are different, it is difficult to reduce the manufacturing cost since two gears that have been separately molded or gear-cut need to be joined, although the noise can be suppressed.
In view of the above, there exists a need for a power transmission device which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
It is a purpose of the present invention to reduce the manufacturing cost while suppressing noise in a fishing-reel power transmission device.
A fishing-reel power transmission device according to the first aspect of the present invention is a device for transmitting power from a first rotating member to a second member in a fishing reel. The fishing-reel power includes a drive gear, a dual-stepped gear, and a driven gear. The drive gear rotates in cooperation with the first member. The dual-stepped gear has a first gear portion that is a helical-tooth gear and meshes with the drive gear, and a second gear portion that is arranged coaxially with the first gear portion and is formed unitarily with the first gear portion as a one-piece unitary member. The second gear portion has one of a straight-tooth gear and a helical-tooth gear having a gear specification such that the lead angle thereof according to which a mold is rotated when molding substantially matches the lead angle of the first gear. The driven gear meshes with the second gear portion of the dual-stepped gear and rotates the second member.
In this power transmission mechanism, as the first member rotates, the drive gear is rotated and the rotation thereof is transmitted to the first gear portion and further from the second gear portion to the driven gear, which then rotates the second member. The first gear of the dual-stepped gear is a helical-tooth gear while the second gear is either a straight-tooth gear or a helical-tooth gear. Where the second gear is the helical-tooth gear, if the orientations of the first and second gear portions are substantially the same, more preferably if the specification thereof is determined such that the lead angles according to which a mold is rotated when molding the first gear portion and the second gear portion substantially match each other, the two gear portions can be simultaneously molded in a single metal mold. Specifically, the lead angles can be represented as follows; the lead angle for the first gear portion is tan xcex1/d1 and that for the second gear portion is tan xcex2/d2, where the diameters of the pitch circles of the first and the second gear portions are d1 and d2, respectively, and the helical-tooth angles are xcex1 and xcex2, respectively. The specification for each gear portion should be decided so that these lead angles match each other. Here, preferably, the pitch circle diameters d1 and d2 are determined from the normal modules M1 and M2 and the numbers of teeth Z1 and Z2 of the respective teeth of the gears, as follows: d1=M1xc3x97Z1/cos xcex1 and d2=M2xc3x97Z2/cos xcex2, respectively. Thus, if the specifications of the gears are designed such that the following equation holds: M1xc3x97Z1/sin xcex1=M2xc3x97Z2/sin xcex2, the lead angles of the two gear portions match each other. By determining the specifications of the two gear portions in such a manner or by making the second gear portion have straight teeth, a dual-stepped gear in which two gear portions are formed unitarily by molding can be easily obtained at low cost. Consequently, in a fishing-reel power transmission device, when both of the gear portions are configured to have helical teeth, the manufacturing cost can be reduced irrespective of the material while suppressing noise. On the other hand, when the second gear portion is configured to have straight teeth, the manufacturing cost can be reduced while suppressing noise by forming the dual-stepped gear of a synthetic resin.
According to the second aspect of the invention, the fishing-reel power transmission device is provided as set forth in the first aspect, in which the dual-stepped gear is made of a synthetic resin. In this case, since the dual-stepped gear is made of a synthetic resin, noise can be suppressed even when the drive gear and the driven gear are made of metal. In addition, noise can be suppressed even when the second gear portion has straight teeth.
According to the third aspect of the invention, the fishing-reel power transmission device is provided as set forth in the first or second aspect, in which the first gear portion has a larger diameter than does the second gear portion. In this case, since the first gear portion, which meshes with the first member, has a larger diameter than the second gear portion, the speed of the rotation of the first member can be reduced by the dual-stepped gear when the rotation is transmitted to the second member.
According to the fourth aspect of the invention, a fishing-reel power transmission device is provided as set forth in any one of first through third aspects, in which the drive gear is made of metal; and the driven gear is made of a synthetic resin. In this case, even when the drive gear is made of metal, noise can be suppressed because the first gear portion, which meshes with it, has helical teeth, and at the same time, even when the second gear has straight teeth, noise can be suppressed because the driven gear is made of a synthetic resin.
According to the fifth aspect of the invention, a fishing-reel power transmission device is provided as set forth in the fourth aspect, in which the second gear portion and the driven gear are straight-tooth gears. In this case, the dual-stepped gear can be easily molded since second gear portion is a straight-tooth gear.
According to the sixth aspect of the invention, a fishing-reel power transmission device is provided as set forth in any one of the first through fifth aspects, in which the number of teeth of the drive gear is less than the number of teeth of the first gear portion, and the number of teeth of the second gear portion is less than the number of teeth of the driven gear. In this case, a great reduction in speed is possible from the drive gear toward the driven gear.
According to seventh aspect of the invention, a fishing-reel power transmission device is provided as set forth in any one of first through sixth aspects, in which the fishing reel being a spinning reel in which the second member that is a rotor being mounted rotatably to a reel unit and being for guiding a fishing line rotates in cooperation with rotation of the first member that is a handle and a spool to which the fishing line is wound reciprocates back and forth in cooperation with rotation of the handle, wherein: the drive gear is a pinion gear to which the rotor is mounted non-rotatably and that meshes with a master gear provided on a rotation shaft of the handle; the driven gear is provided for an oscillating mechanism for reciprocating the spool back and forth; and the first gear portion meshes with the pinion gear.
In this case, when the device is used as a device for decelerating a traverse cam type oscillating mechanism of a spinning reel also, it is possible to reduce the manufacturing cost while suppressing noise.
These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.